The present invention relates to a slidable gate valve for powder and granular material that actuates a gate to open and close a powder and granular material transport path, and more specifically a sealing construction of the slidable gate valve.
A prior art slidable gate valve 501 for powder and granular material is shown in FIGS. 15 and 16. A frame body 504 has an opening 503 and includes an inlet hopper 540 and an outlet hopper 542 linked with each other by a base frame 544. A gate plate holder 546 for receiving a gate plate 502 connecting with an air cylinder 505 is joined with the frame body 504. The air cylinder 505 is further joined with the gate plate holder 546. A sealing member 509 (for example, including a gland packing) is attached to one end of the gate plate holder 546 to seal the gate plate 502 from the gate plate holder 546. A guide rail 513 is formed below the inlet hopper 540 to guide the gate plate 502. The air cylinder 505 extends the gate plate 502 to close the opening 503, while contracting the gate plate 502 to open the opening 503. This arrangement accordingly opens and closes a vertical transport path of powder and granular material. The slidable gate valve 501 for powder and granular material is connected to external air equipment and power equipment.
The rectangular gate valve is used for square and rectangular exhaust ports and is applicable for discharge of powder and granular material from conveyors or reservoirs. The circular gate valve is used for circular exhaust ports and is applicable for discharge of powder and granular material from silos and check bottles. The simple and easily-maintained sealing mechanism suitable for the respective applications is adopted for the enhanced sealing property.
Although there is a seal of the clearance between the gate plate holder 546 and the frame body 504, sealing of the moving path of the powder and granular material from the outside is still insufficient. There is a clearance between the gate plate 502 and the lower end of the inlet hopper 540 in the frame body 504 in order to prevent potential troubles, for example, to reduce the friction resistance of the gate plate 502 for the smooth sliding movement and to ensure the sufficient strength of the gate plate 502 for supporting the pressure of the accumulating powder and granular material. Even in the closed state of the gate plate 502, the powder and granular material are leaked down through the clearance. The insufficient sealing property in the moving path of the powder and granular material causes problems, such as leakage of the air and powder and granular material. The positive pressure in the upper area of the gate plate 502 results in a worse leakage.
The object of the present invention is thus to prevent leakage of powder and granular material in its moving path in a closed state of a gate plate, as well as leakage of powder and granular material out of the moving path in the course of opening and closing the gate plate.
In order to attain at least part of the above and other related objects, the present invention is directed to a slidable gate valve for powder and granular material, which includes: a frame body with an opening; an actuator attached to the frame body; a holder case connected to the frame body; a gate plate that is slid by the actuator in a direction perpendicular to a moving path of the powder and granular material, so as to open and close the opening; a ring-shaped sealing member that is attached to a through hole formed in a specific area of the frame body on a side of the holder case and seals the gate plate from the frame body, so as to prevent leakage of the powder and granular material out of the moving path; and a support member that supports the gate plate, wherein the sealing member includes a seal pressed into a seal housing with a step. This arrangement gives a variation in sealing pressure and thus effectively prevents leakage of the powder and granular material out of the moving path. The holder case may receive the slidable gate plate and accommodate an electric part and a hydraulic part. The support member may support the gate plate in the closed state or may be constructed like a guide rail to guide the sliding motion of the gate plate. The seal housing may have one or multiple steps.
In one preferable application of the slidable gate valve for powder and granular material as described above, the seal housing has a ring-shaped face inclined relative to a direction of the sliding movement of the gate plate. This arrangement gives a place-dependent variation in sealing pressure and thereby more effectively prevents leakage of powder and granular material out of the moving path.
In another preferable application of the slidable gate valve for powder and granular material as described above, the slidable gate valve further includes a second sealing member to seal a clearance between the frame body and the gate plate in the closed state of the opening and thereby prevent leakage of the powder and granular material in the moving path. This arrangement effectively prevents leakage of powder and granular material out of the moving path as well as in the moving path. The second sealing member is required to prevent leakage when the powder and granular material are fine powder, but may not be required when the powder and granular material are rough powder or granular material sufficiently large in size relative to the clearance. The second sealing member is, for example, a polymer material having a triangular or rectangular cross section and preferably has a labyrinth seal structure for the enhanced sealing property, although not essential.
The present invention is also directed to another slidable gate valve for powder and granular material, which includes: a frame body with an opening; an actuator attached to the frame body; a holder case connected to the frame body; a gate plate that is slid by the actuator in a direction perpendicular to a moving path of the powder and granular material, so as to open and close the opening; a sealing member that includes a packing pressed into a seal housing attached to a through hole formed in a specific area of the frame body on a side of the holder case and seals the gate plate from the frame body, so as to prevent leakage of the powder and granular material out of the moving path; and a support member that supports the gate plate, wherein the actuator is an air cylinder, and exhaust of the air cylinder is induced into the seal housing. The exhaust discharged in the course of actuation of the gate plate by the air cylinder raises the pressure in the seal housing and thus more effectively prevents leakage of powder and granular material out of the moving path. The sealing member may have any adequate construction.
The present invention is further directed to still another slidable gate valve for powder and granular material, which includes: a frame body with an opening; an actuator attached to the frame body; a holder case connected to the frame body; a gate plate that is slid by the actuator in a direction perpendicular to a moving path of the powder and granular material, so as to open and close the opening; a first sealing member that is attached to a specific area of the frame body on a side of the holder case and seals the gate plate from the frame body, so as to prevent leakage of the powder and granular material out of the moving path; a support member that supports the gate plate; and a second sealing member that seals a clearance between the frame body and the gate plate in the closed state of the opening with the gate plate, wherein a certain area of the second sealing member, which is in contact with the gate plate, forms a labyrinth seal structure to prevent leakage of the powder and granular material in the moving path. Invading powder and granular material are trapped by the labyrinth seal structure to enhance the sealing property and thus effectively prevent leakage of powder and granular material in the moving path. The first sealing member may be a ring-shaped gland packing or may be a packing or another seal pressed into a seal housing with multiple steps.
In one preferable embodiment of the slidable gate valve for powder and granular material in accordance with the present invention as described above, the support member includes a guide rail that props up and guides the gate plate and is attached to the frame body to be extended in a direction of the sliding movement, and the gate plate is interposed and slid between the sealing member and the guide rail to open and close the opening. This arrangement effectively attains the object described above, and besides prevents the gate plate in the closed state from being bent due to load of the powder and granular material accumulating on the gate plate, thus attaining the enhanced strength and the improved durability. The structure of this embodiment ensures smooth sliding movement of a relatively large-sized gate plate.
In another preferable embodiment of the slidable gate valve for powder and granular material of the present invention as described above, the support member includes at least two projections that are disposed in an inner area of the frame body and prop up the gate plate when the gate plate closes the opening. This arrangement effectively attains the object described above, and supports the gate plate in the closed state, so as to prevent the gate plate in the closed state from being bent due to load of the powder and granular material accumulating on the gate plate, thus attaining the enhanced strength and the improved durability.